MSE has NEVER been good. It has always been reviewed and failed all the testing. NEVER rely on MSE.
Secondly Windows 7/8 are no longer supported. Many games and other services will NOT be working or coded for W7/8 based systems. You still have the opportunity to update FREE to W10 while you can or else you will have to buy it to play games and use services.
What do I men by services? Well many security systems they implement for websites (like streaming sites) require you to have some things on your computer, those are ONLY available on the latest edition of Windows (not being released for NON-supported Windows editions).
PCs are NOT gaming consoles, they are like cars, which means ALOT... I MEAN ALOT.. of maintenance is needed on them to keep them going, and two key elements if proven working Antivirus and Malware. Even "just gaming" doesn't matter, because any WEBSITE (aka a forum, etc.) can be infected and 'push' the code when you access the website infecting your system. Never mind if you share a USB drive or access your email ever.
The best FREE ones I seen are Avira, AVG, Panda for Antivirus, and Malwarebytes (you have to run the scan manually I suggest monthly) all easily downloaded from www.filehippo.com .